A rubber manhole cover, suitable for attaching to a top of a metal manhole lid, includes at least two bonded layers of rubber material of differing properties, including a bottom layer of a first rubber material, and a top layer of vulcanized rubber material, the top and bottom layers functioning as a single unit.
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17. A rubber manhole cover, suitable for attaching to a top of a metal manhole lid, comprising:
at least two bonded layers of rubber material of differing properties, including a bottom layer of first rubber material, and a top layer of vulcanized rubber material, the top and bottom layers functioning as a single unit.
11. A manhole cover system, comprising:
a manhole lid of metal, disposed below an elevation of surrounding pavement; and
a cover, attached atop the manhole lid, comprising at least two bonded layers of rubber material of differing properties, the cover having an overall thickness sufficient to substantially match the elevation of the surrounding pavement.
1. A manhole cover device, comprising:
a bottom layer of rubber material, suitable for attaching to a top of a metal manhole lid, having a top surface; and
a first top layer of vulcanized rubber material, having different material properties than the bottom layer, the top layer being affixed to the top surface of the bottom layer, the top and bottom layers functioning as a single unit.
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1. Field of the Invention
The present invention relates generally to manhole covers. More particularly, the present invention relates to a resilient pad that is attachable to a manhole cover.
2. Related Art
Manholes are common structures in streets and roadways for allowing access to underground utilities such as water and sewer lines or stored materials or equipment. Manholes provide an opening to allow workmen to descend beneath the surface to obtain access to these underground items. Manholes and manhole covers are typically subject to significant loads, such as the weight of roadway vehicles and impact loads from them, and thus must be made of strong and durable materials. The top of a manhole typically includes a strong metal (e.g. cast iron) frame having a projecting ledge around the circumference of the opening, with a heavy cast iron cover that rests on the ledge and closes the manhole. The cover is designed to support surface loads, and the frame transmits those loads to the underground supporting structure. Manhole covers are generally made heavy to resist unintentional opening or vandalism, and in many cases are bolted down in order to make the installation water tight and tamper-proof.
One challenge associated with manhole installations is maintaining the manhole cover flush with a surrounding roadway elevation. When a street is repaved, the pavement elevation increases by a few inches. Manholes can also settle over time, producing an elevation difference with surrounding pavement. If these conditions are not corrected, the manhole location can present a road hazard, the manhole cover and supporting structure will be subjected to increased impact loads from passing vehicles, and the surrounding pavement is likely to degrade more quickly. To avoid these problems, road paving crews sometimes simply pave over an existing manhole. Unfortunately, this defeats the whole purpose of the manhole, and hides its location from view.
More commonly, when a street is repaved or a manhole has settled, existing manholes in the street are typically raised to match the elevation of the pavement. This process typically involves the installation of new grade rings or other structures atop the manhole frame to raise its elevation, and may also involve the installation of a new concrete collar surrounding the manhole to reinforce the transition from asphalt pavement to the rigid cast iron manhole top. Unfortunately, raising manholes in a street can be an expensive and time-consuming process, thus adding to the financial burden that highway maintenance agencies face in building and maintaining roadways.
It has been recognized that it would be advantageous to develop a system for raising manhole elevations that is simple and inexpensive.
It has also been recognized that it would be advantageous to have a manhole grade adjustment system that makes manhole covers more useful.
In accordance with one embodiment thereof, the present invention provides a manhole cover device that includes a bottom layer of rubber material, suitable for attaching to a top of a metal manhole lid, having a top surface, and a first top layer of vulcanized rubber material, having different material properties than the bottom layer. The top layer is affixed to the top surface of the bottom layer, the top and bottom layers functioning as a single unit.
In accordance with another embodiment thereof, the invention provides a manhole cover device for attachment to a metal manhole lid, including a manhole lid of metal, disposed below an elevation of surrounding pavement, and a cover, attached atop the manhole lid. The cover includes at least two bonded layers of rubber material of differing properties, and has an overall thickness sufficient to substantially match the elevation of the surrounding pavement.
In accordance with yet another embodiment thereof, the invention provides a rubber manhole cover, suitable for attaching to a top of a metal manhole lid. The rubber manhole cover includes at least two bonded layers of rubber material of differing properties, including a bottom layer of a first rubber material, and a top layer of vulcanized rubber material, the top and bottom layers functioning as a single unit.
Additional features and advantages of the invention will be apparent from the detailed description which follows, taken in conjunction with the accompanying drawings, which together illustrate, by way of example, features of the invention, and wherein:
Reference will now be made to exemplary embodiments illustrated in the drawings, and specific language will be used herein to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Alterations and further modifications of the inventive features illustrated herein, and additional applications of the principles of the inventions as illustrated herein, which would occur to one skilled in the relevant art and having possession of this disclosure, are to be considered within the scope of the invention.
As noted above, the relative elevation between a manhole cover and surrounding pavement can change due to settlement of a manhole or repaving of a street. In some cases manhole covers are simply paved over when a road is resurfaced. This is not only annoying for drivers and damaging to pavement, but it also hinders access to the manhole. Workers must chip away the pavement before opening the manhole cover, leaving a pothole in the surface. For these and other reasons there is often a need to raise existing manholes to match the elevation of the surrounding pavement. This ordinarily involves some digging in the road to install new manhole rings or other relatively expensive devices to bring the manhole cover up to the new grade level.
Advantageously, the inventors have developed a simple and relatively inexpensive system for adjusting the grade of existing manholes. Shown in
Typical manhole lids, like the manhole lid 12 shown in
In order to allow the manhole cover to be adjusted to grade easily, the present invention provides a manhole cover device 32. The manhole cover device is a durable cover or pad, indicated generally at 34, that attaches to the top of the cast iron manhole lid to approximately match the level of the surrounding pavement. Cross-sectional views of various manhole structures having manhole lids provided with various embodiments of a manhole pad or cover in accordance with the present disclosure are provided in
As shown in
The manhole pad or cover 34 includes at least two layers of resilient material, such as rubber, or rubber-like material. The pad has a bottom layer 42 of one type of material, and at least one top layer 44 of a different type of material. The top and bottom layers can be affixed together with chemical adhesive, such as industrial strength sag resistant adhesive, rubber-to-rubber adhesive, fasteners, such as large staples, or cement type adhesives. The bottom layer can be of a relatively soft rubber material, and the top layer can be of a harder and/or more durable material. This multi-ply configuration provides several advantageous features. The bottom layer can be of recycled rubber, which is relatively inexpensive. Other materials, such as neoprene, can also be used. The bottom layer can be soft enough to deform around the lugs 22, protrusions, indicia 24, and other irregularities in the manhole lid 12. The bottom layer can be made out of recycled rubber. The bottom layer can have a durometer of about 60+/−5 Shore A, hardness of 60 lb/ft, compression recovery of about 98%, and tensile strength of about 300 psi. Other materials that can be used include various rubber combinations, such as butyl rubber, chlorobutyl, epichlorhydrin, ethylene propylene rubber, hydrogenated nitrile rubber, natural rubber, nitrile rubber, polychloroprene, polyurethane rubber, and styrene butadiene rubber.
The top layer 44, on the other hand, can be of a vulcanized rubber material that is more durable under the wear and tear of roadway traffic. In one embodiment, the top layer is neoprene (polychloroprene) rubber. In another embodiment, the top layer can be a blend of SBR (styrene butadiene rubber), CR (neoprene) and NBR (nitrile) rubbers, which gives it a 55-65 durometer, minimum tensile strength of 725 psi, temperature range of −40° to 200° F. Resistance to UV radiation is also desirable for the top layer. Accordingly, materials can be selected that have a high EPDM, making the top layer UV resistant. Other rubbers which can be used include butyl rubber, chlorobutyl, epichlorhydrin, ethylene propylene rubber, hydrogenated nitrile rubber, natural rubber, nitrile rubber, polychloroprene, polyurethane rubber, and styrene butadiene rubber. More durable vulcanized rubber materials tend to resist deformation around deformities beneath them, but are durable against wear and the elements, and provide a non-skid surface. Recycled rubber materials, on the other hand, more readily conform to, even grind into irregularities, but are less durable and resistant to the elements. Using these two types of layers together allows the bottom layer to smooth out the irregularities, and provide a smooth durable top surface.
Having two layers also helps resist curling or warping of the pad 34. Single ply vulcanized rubber pieces have a tendency to curl at the edges, due to internal stresses created during the vulcanization process. A manhole cover that curls at the edges is not only unsightly, but can present a road hazard, and can wear out faster than one that is flat. Additionally, pads that are curled up at the edges can be pulled up or torn up by a snowplow or the like, and can be prone to vandalism. The multi-ply configuration disclosed herein reduces curling and warping by adhering the curl-prone vulcanized top layer 44 to a bottom layer 42 of material that is not as prone to warping. The bottom layer thus helps resist the tendencies of the top layer, and keeps the whole assembly more flat.
The relative thicknesses of the top and bottom layers 44, 42, can vary. As shown on the left side in
More than two layers can also be provided, and these can be in various configurations and thickness combinations. For example, shown on the right side of
The manhole pad or cover 34 can be attached to the manhole lid 12 using mechanical fasteners or chemical adhesive. For example, shown on the left side of
The manhole cover 34 can be of different shapes and sizes, and can be used in a variety of installation conditions. The manhole pad shown in
The size of the manhole cover can also vary. For example, shown on the left side of
In another embodiment, shown on the right side of
The configuration shown on the left side of
Shown on the right side of
The manhole pad or cover 34 can be provided in a number of other variations, too. For example, rather than being intended to deform around irregularities in the top surface of a manhole lid (e.g. lugs 22 in
Another feature that is provided by the manhole cover disclosed herein is that the pads 34 provide a location for useful or desirable indicia. The manhole covers or pads disclosed herein can have alphanumeric characters, linguistic characters, ornamental designs, marks, logos, visual targets, or any other type of indicia provide on their top surface. For example, shown in
Other examples of indicia are shown in
The method for applying indicia to the manhole cover pad can vary. It will be apparent that paints or pigments can be used. Advantageously, the configuration of the manhole cover pad 34 disclosed herein lends itself to a more durable method for providing desired indicia by providing rubber inlays of contrasting color to produce words, letters, logos, etc. The top layer 44 of rubber material can be cut and material removed to create cutouts of any desired shape inside the boundary of the manhole cover. Corresponding pieces of the exact size and shape of the cutouts can be cut from other pieces of rubber having the same thickness and a contrasting color. Highly accurate cutting of the cutouts and the inlay pieces can be done using water jet cutters and other cutting devices that are well known and widely available. The inlay pieces can then be inlaid into the cutouts in the manhole cover pad, and the cover with the contrasting color inlay pieces can then be vulcanized as a unit, fusing the inlays and surrounding material into an integral unit. This method provides the desired indicia as integrally vulcanized color inlays in a single manhole cover pad. The indicia will be highly durable because they are integral with the material of the top layer of the cover, and will provide the desired shape and color over the life of the manhole cover, even as the top surface wears.
Cross-sectional views of top layers 44 having inlaid pieces are shown in
This manhole cover disclosed herein thus provides a durable, non-skid surface, and eliminates the need for more expensive grade rings or other devices to bring a manhole lid up to grade. The manhole cover can be attached to a manhole lid using mechanical fasteners or adhesive, and comprises multiple layers, thus helping it remain geometrically stable while also being economical and easily conformable to the shape of the top of the underlying manhole lid. Decorative and/or functional indicia can be provided on the top surface of the manhole cover, such as with rubber inlays, thus giving the pad an additional function in a durable configuration.
It is to be understood that the above-referenced arrangements are illustrative of the application of the principles of the present invention. It will be apparent to those of ordinary skill in the art that numerous modifications can be made without departing from the principles and concepts of the invention as set forth in the claims.
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